Apparatuses and methods of testing biological fluids, as well as test elements for use in such apparatuses, are well known. For example, electrochemical testing methods are known that generally rely upon a correlation between a current (amperometry), a potential (potentiometry), or an accumulated charge (coulometry) and an analyte concentration, typically in conjunction with a reagent that produces charge-carriers when combined with the analyte. Known test elements for conducting electrochemical tests can be disposable test strips having a reagent that chemically reacts with the analyte of interest in a biological fluid sample. Generally, test elements are attached to or inserted into a test meter that can measure the reaction between the analyte and the reagent to determine the analyte concentration.
In general, test elements have a reaction zone containing measurement electrodes that directly contact the biological fluid sample. In some known amperometric and coulometric electrochemical measurement systems, the measurement electrodes are attached to electronic circuitry in the test meter that supplies an electrical potential to the measurement electrodes and measures the response of the electrochemical test element to this potential (e.g., current, impedance, charge, etc.). This response is proportional to the analyte concentration.
Robust monitoring and confirmation of fill of a capillary channel at the reaction zone is important for test elements with a capillary channel that is open on two or more sides. Such test elements have multiple direction filling capabilities since they may be dosed by the user along any open edge or at a corner. As such, fill location, sufficiency and time can vary depending on use variation by the user of the test element. Some known test elements, however, can give an inaccurate indication that a sufficient sample of the biological fluid has been obtained due to a progression of the biological fluid into, down or across the capillary channel of the test element. Such inaccurate indications can result in biased and/or inaccurate test results. Accordingly, a need exists for improved detecting, monitoring and confirming of the presence and progress of an adequate biological fluid sample volume for a successful analyte concentration or presence measurement by test elements.